(a) Field of the Invention
The present invention relates to an optical printed circuit board (PCB) and an optical interconnection block using an optical fiber bundle. More specifically, the present invention relates to an optical printed circuit board with a built-in optical waveguide, and an optical interconnection block in optical PCB based optical interconnectors.
(b) Description of the Related Art
In general, a printed circuit board (PCB) represents a phenol-resin or epoxy-resin circuit board on which various components are mounted and paths for interconnecting the components are fixedly printed. As to a PCB manufacturing process, a thin film of copper is attached to one side of a phenol-resin insulation board or an epoxy-resin insulation board, the thin film is etched according to predetermined patterns to configure a desired circuit, and holes for mounting components are generated.
The PCB can be classified as a single layer substrate, a double layer substrate, and a multi-layered substrate, and the multi-layered substrates are used in high-precision products because the increased layers allows more installation capacity. A multi-layered PCB represents a printed circuit board having conductive patterns on at least three layers that are separated by insulation matter.
The copper film is patterned to form an inner layer and an outer layer on the PCB in the conventional PCB manufacturing process, but high polymers and glass fibers have been recently used to insert optical waveguides into the PCB, which is referred to as an electro-optical circuit board (EOCB). The EOCB has optical waveguides and glass substrates in addition to the copper circuit patterns and allows both electrical signals and optical signals so that the EOCB may interface very high-speed data communication executed on the same board by using optical signals and may convert the optical signals into electrical signals and store data or process signals.
Various coupling methods for connecting the optical signals on the multi-layered PCB have been proposed, and general multi-channel interconnection methods include the direct writing method, the beam reflection method, the reflection mirror using method, and the direct coupling method.
FIG. 1 shows a conventional optical PCB and an optical connection structure using an optical interconnection block.
Referring to FIG. 1, a via hole is generated in the optical PCB 1, and an optical connection rod 4 having a reflection mirror with the angle of 45° on the top thereof is inserted into the via hole. In this instance, the reflection mirror is formed by coating silver (Ag) or aluminum (Al) on the optical connection rod 4, or the same is configured by attaching an additional reflection mirror thereon. Light beams output by a light source of an optical transmitter are reflected by 90° on the mirror with the angle of 45° to be transmitted through an optical waveguide 2 to a mirror with the angle of 45° of the optical connection rod 4 at the side of an optical receiver, and the light beams, again reflected by 90° on the mirror, are transmitted to a photo-detector 6 of the optical receiver.
For example, when electrical signals are applied to the optical transmitter by a process board, the electrical signals are converted into optical signals by a laser diode 5, the optical signals are transmitted through a lens to the left reflection mirror to be reflected, the reflected optical signals are provided through the optical waveguide to the right reflection mirror to be reflected again, and the reflected optical signals are transmitted through another lens to a photodiode 6 functioning as a photo-detector in the optical receiver. In this instance, the optical waveguide transmits the light beams through a multi-mode polymer waveguide core with low loss, and a waveguide clad is formed around the core. Therefore, the electrical signals provided by the left processor board are converted into optical signals and transmitted to the right processor board, and are then converted into electrical signals again.
In the prior art, when the vertical cavity surface emitting laser (VCSEL) 5 emits light, a micro-lens gathers the light and transmits the same to the optical waveguide through a PCB hole or an optical via hole 3, and the light is transmitted to another layer through the hole. A silicon optical bench (SiOB) generally referred to as a silicon wafer is formed on the PCB 1, and a polymer substrate can be used for the SiOB. The optical waveguide transmits the light provided by the VCSEL through the lens to another optical waveguide on another layer.
The VCSEL represents a light source for vertically outputting laser beams on a substrate and is used to transmit and amplify optical data. LEDs and edge emitting laser diodes (LDs) have been widely used as the light sources, although surface-emitting lasers (SELs), developed in the nineties, have recently come to be used instead of the LEDs and the edge emitting LDs. The VCSELs are used for optical fiber communication, interface, and parallel processing of large amounts of information.
FIGS. 2A and 2B show conventional optical interconnection blocks configured by optical interconnectors for transmitting light beams of various channels in parallel.
Referring to FIG. 2A, the optical interconnection block includes a plurality of optical connection rods 8 in parallel, each having a mirror 10 with the reflection angle of 45°. Vertical light beams 11 output from the light source of the transmitter or input to the photo-detector of the receiver are input to/output from the side 9 of the transmitter of the optical connection rod 8, and the light beams are reflected on the mirror 10 by the angle of 90°, and are then horizontally transmitted through the optical waveguide 2 of the optical PCB 1 of FIG. 1.
Referring to FIG. 2B, the optical interconnection block includes a plurality of parallel optical connection rods 8 bent by the angle of 90°. Vertical light beams 17 output from the light source of the transmitter or input to the photo-detector of the receiver are input to/output from the side 15 of the transmitter of an optical fiber 14, and the light beams are horizontally transmitted through the optical fiber 14 and are transmitted through the optical waveguide 2 of the optical PCB 1 of FIG. 1.
However, it is difficult to accurately match the position of the optical fiber 8 or 14 in the optical interconnection block with the position of the optical waveguide 2 of the optical PCB 1 since the optical interconnection blocks are connected with a single optical fiber for each optical signal channel. That is, it is difficult to control an optical path when the optical paths, in the order of the light source 5 of the transmitter←→the optical fibers 8 and 14 in the optical interconnection block ←→the optical waveguide 2 in the optical PCB ←→the optical fibers 8 and 14 ←→the photo-detector 6 of the receiver, cross each other and the light beams are provided to an adjacent channel.